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Significant wave height and Douglas scale - are not the same

Significant wave height and Douglas scale are two very different measures of sea conditions. If C/P contains reference to both then which one prevails? Question came up in London Arbitration 06/19.

Charterers contended that vessel lost time and over-consumed FO, and presented wx reports by AWT showing that there were many good wx periods. Owners argued that there were no good wx days and ships log books evidenced that.

C/P defined good wx as "significant wave height confined to limits of DOUGLAS sea state 3 (0.5-1.25m)……and should there be a discrepancy between vessel’s logs and oceanroutes, both parties shall discuss to assess nature of discrepancies for a mutual agreement.”

Significant wave ht is a measure of the highest third of waves encountered, whereas Douglas scale refers to a range. Charterers referred to an article by AWT which interpreted swell ht for Douglas scale 3 to be 2m. Owners said that waves could not be higher than 1.25m.

Tribunal accepted that there exists no established relationship between significant wave ht and Douglas Scale. After considering position of both parties, it chose to go with owners' view (...resulting in slight conflict with Arb. 12/14!). Also, since mutual agreement clause was unworkable, tribunal held that ship’s logs best represent the weather.

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